Lithium ion conductive glass-ceramics comprise in mol %:

                P.sub.2 O.sub.5               30-45%
                SiO.sub.2                      0-15%
                GeO.sub.2 + TiO.sub.2         25-50%
                in which  GeO.sub.2            0-50%
                          TiO.sub.2            0-50%
                ZrO.sub.2                        0-8%
                M.sub.2 O.sub.3                     0<-10%

where M is an element or elements selected from the group consisting of In, Fe, Cr, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb and Lu

                    Al.sub.2 O.sub.3       0-12%
                    Ga.sub.2 O.sub.3       0-12%
                    Li.sub.2 O            10-25%

and contain Li.sub.1+X (M, Al, Ga).sub.X (Ge.sub.1-Y Ti.sub.Y).sub.2-X (PO.sub.4).sub.3 (where 0 Bestaat uit de ionen geleidende glas-keramiek van het lithium in mol %: P.sub.2 O.sub.5 30-45% SiO.sub.2 0-15% GeO.sub.2 + TiO.sub.2 25-50% in welke GeO.sub.2 0-50% TiO.sub.2 0-50% ZrO.sub.2 0-8% M.sub.2 O.sub.3 0 waar M een element of elementen die uit de groep binnen bestaan uit, Fe, Cr, Sc, Y, La, Ce, PR, Nd, Sm, de EU, GD, Th, Dy, Ho, ER, Tm, Yb en Lu wordt geselecteerd die is Al.sub.2 O.sub.3 0-12% Ga.sub.2 O.sub.3 0-12% Li.sub.2 O 10-25% en bevat Li.sub.1+X (M, Al, Ga).sub.X (ge.sub.1-Y ti.sub.Y).sub.2-X (PO.sub.4).sub.3 (waar 0